Nantharak K. Development of academic achievement in mathematics regarding addition and subtraction of students in Prathom 2 at Ban Na Khae School. using skill training. jlsid [internet]. 2024 Dec. 5 [cited 2026 Sep. 11];1(1):9-20. available from: https://so19.tci-thaijo.org/index.php/ajld/article/view/1191